import java.util.Arrays;

/**
 * @Author 12629
 * @Description：
 */
public class MyStack {
    private int[] elem;
    private int usedSize;

    private static final int DEFAULT_CAPACITY = 10;

    public MyStack() {
        this.elem = new int[DEFAULT_CAPACITY];
    }
    /*private int[] extendArray(int[] elem) {
        return Arrays.copyOf(elem,elem.length*2);
    }*/

    public void push(int val) {
        /*if(elem.length == usedSize) {
            elem = extendArray(elem);
        }
        elem[usedSize] = val;
        usedSize++;*/
        if(isFull()) {
            elem = Arrays.copyOf(elem,2*elem.length);
        }
        elem[usedSize] = val;
        usedSize++;
    }
    public boolean isFull() {
        return usedSize == elem.length;
    }

    public int pop() {
        if(isEmpty()) {
            throw new EmptyException();
        }
        int oldVal = elem[usedSize-1];
        usedSize--;
        return oldVal;
    }

    public int peek() {
        if(isEmpty()) {
            throw new EmptyException();
        }
        return elem[usedSize-1];
    }

    public boolean isEmpty() {
        return usedSize == 0;
    }
}
